1. Field of the Invention
The present invention relates generally to a vane-type rotary compressor for use in, for example, an automotive air conditioner and, in particular but not exclusively, to an improvement of shaft seal parts mounted in a vane-type rotary compressor.
2. Description of Related Art
FIG. 1 depicts a conventional vane-type rotary compressor that includes a cylinder 1 having a cylindrical inner surface, a rotor 4 rotatably mounted in the cylinder 1, and front and rear covers 7, 8 secured to opposite ends of the cylinder 1, respectively, to define a compression chamber 9 therebetween. The front cover 7 accommodates only one shaft seal part 13 and has a bypass passage 16 defined therein so as to extend therethrough. The bypass passage 16 opens at one end thereof to a space defined between a bearing 11 and the shaft seal part 13 and at the other end thereof to a minute space defined between the rotor 4 and the front cover 7 at a suction stroke portion of the compression chamber 9.
In the above-described construction, because the bypass passage 16 opens to the suction stroke portion, a refrigerant containing a lubricant passes a space between the bearing 11 and a drive shaft 10 and is led to the shaft seal part 13 and then to the suction stroke portion via the bypass passage 16, supplying the bearing 11 and the shaft seal part 13 with the lubricant.
In this construction, however, it is impossible to prevent the shaft seal part 13 from communicating with a compression stroke portion of the compression chamber 9. Accordingly, a pressure substantially equal to the discharge pressure acts on the shaft seal part 13, increasing the temperature and pressure around the shaft seal part 13. To ensure the reliability of component parts of the shaft seal part, a relatively complicated construction is required.